Isomeric Molecular Rectangles Resulting from Self-Assembly of

Inorg. Chem. 2006, 45, 2501−2508

Isomeric Molecular Rectangles Resulting from Self-Assembly of Dicopper Complexes of Macrocyclic Ligands Anna Company,† Laura Go´mez,† Josep Maria Lo´pez Valbuena,† Ruben Mas-Balleste´,‡ Jordi Benet-Buchholz,§ Antoni Llobet,*,| and Miquel Costas*,† Departament de Quı´mica, UniVersitat de Girona, Campus de MontiliVi, E-17071 Girona, Spain, Department of Chemistry, UniVersity of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, Institut Catala` d’InVestigacio´ Quı´mica (ICIQ), AVinguda Paı¨sos Catalans, 16 Campus UniVersitari, E-43007 Tarragona, Spain, and Departament de Quimica, UniVersitat Autonoma de Barcelona, Bellaterra, E-08193 Barcelona, Spain Received October 11, 2005

Dinuclear copper complexes containing hexaazacyclophane macrocyclic ligands react with the disodium salt of terephthalic acid resulting in the self-assembly of rectangular molecules with the general formula [(Cu2L)2(p-(O2CC6H4CO2)2)]X4, where X ) CF3SO3 and ClO4 (3X4, L ) Me2p and 4X4, L ) Me2m). Tetranuclear complexes 3(CF3SO3)4 (as polymorphs 3a and 3b) and 4(ClO4)4 have been characterized by single-crystal X-ray diffraction analysis providing definitive proof of their structure as well as their metrical parameters. 3a contains, in its unit cell, two isomeric cationic units (3asyn and 3aanti) that differ in the relative position of the two O carboxylate atoms which bind to the Cu atoms of the different macrocyclic complexes, leading to boxes with different metrical parameters. ESI-MS analyses of solutions of the tetranuclear complexes 3(CF3SO3)4 and 4(CF3SO3)4 exhibit cluster ions which match the solid state formulation, thus demonstrating that the cages are retained in solution.

Introduction Self-assembly processes and their regulation by selfrecognition mechanisms are important topics because of their implication in biology, chemistry, and materials science.1-10 Hydrogen-bonding and metal-ligand interactions are among the most powerful directing forces for the self-assembly processes which allow the construction of large suprastruc* Authors to whom correspondence should be addressed. Fax: 34-972418150 (M.C.); 34-935-813-101 (A.L.). E-mail: [email protected] (M.C.); [email protected] (A.L.). † Universitat de Girona. ‡ University of Minnesota. § Institut Catala ` d’Investigacio´ Quı´mica. | Universitat Autonoma de Barcelona. (1) Fiedler, D.; Leung, D. H.; Bergman, R. G.; Raymond, K. N. Acc. Chem. Res. 2005, 38, 349-358. (2) Rebek, J., Jr. Angew. Chem., Int. Ed. 2005, 44, 2068-2078. (3) Reinhoudt, D. N.; Crego-Calama, M. Science 2002, 295, 2403-2407. (4) Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed. 2001, 40, 20222043. (5) Greig, L. M.; Philp, D. Chem. Soc. ReV. 2001, 30, 287-302. (6) Fiammengo, R.; Crego-Calama, M.; Reinhoudt, D. N. Curr. Opin. Chem. Biol. 2001, 5, 660-673. (7) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. ReV. 2000, 100, 853907. (8) Morgan Conn, M.; Rebek, J., Jr. Chem. ReV. 1997, 5, 11647-1668. (9) Lehn, J.-M. Supramolecular Chemistry; VCH: New York, 1995. (10) Lehn, J.-M. Angew. Chem., Int. Ed. 1988, 27, 89-112.

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tures. In particular, such interactions have allowed the development of discrete cyclic nanostructures containing metal centers, which hold potential use in molecular recognition, photophysics, and catalysis.1,2,11-14 To date, CuI, PdII, and PtII constitute the most common metal ions of choice for this purpose, though a handful of other transition metals have been occasionally described.4,7,9,10,12,14 Reports on supramolecular structures resulting from the self-assembly of CuII complexes appear to be rarer. This is presumably because of the odd d9 ion configuration, which tends to favor asymmetric coordination geometries. These irregular shapes are more difficult to integrate into regular frameworks.15-20 Yet, macrocyclic complexes based on crown ethers or (11) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem. Res. 2005, 38, 369-378. (12) Thanasekaran, P.; Liao, R.-T.; Liu, Y.-H.; Rajendran, T.; Rajagopal, S.; Lu, K.-L. Coord. Chem. ReV. 2005, 249, 1085-1110. (13) Seidel, S. R.; Stang, P. J. Acc. Chem. Res. 2002, 35, 972-983. (14) Angaridis, P.; Berry, J. F.; Cotton, F. A.; Murillo, C. A.; Wang, X. J. Am. Chem. Soc. 2003, 125, 10327-10334. (15) Caradoc-Davies, P. L.; Hanton, L. R. Dalton Trans. 2003, 9, 17541758. (16) Field, L. M.; Lahti, P. M. Inorg. Chem. 2003, 42, 7447-7454. (17) Lai, S.-W.; Drew, M. G. B.; Beerand, P. D. J. Organomet. Chem. 2001, 637-639, 89-93. (18) Maverick, A. W.; Ivie, M. L.; Waggenspack, J. H.; Fronczekand, F. R. Inorg. Chem. 1990, 29, 2403-2409.

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Company et al. Table 1. Crystallographic Data for 1(CF3SO3)4, 2(CF3SO3)4, 3a(CF3SO3)4, 3b(CF3SO3)4, and 4(ClO4)4

empirical formula fw cryst syst space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 formula units/cell temp, K λ(Mo KR), Å Fcalcd, g cm-3 Θmax, deg reflns measured unique reflns param µ, mm-1 R1,a wR2b [I > 2σ (I)] R1,a wR2b (all data) GOF (F2)

1(CF3SO3)4

2(CF3SO3)4‚2CH3CN

3a(CF3SO3)4‚xCH3CN

C32.5H46Cu2F8N6O10S4 1088.07 orthorhombic Cmcm 14.2529(8) 26.1686(18) 27.4119(16) 90 90 90 10 224.0(11) 4 153(2) 0.710 73 1.414 31.57 66 074 8473 [Rint ) 0.1669] 510 1.076 0.1044, 0.2751

C46H68Cu2F12N12O12S4 1464.44 triclinic P1h 10.6473(10) 12.4122(12) 14.1083(14) 64.789(3) 75.012(4) 65.012(4) 1521.9(3) 1 153(2) 0.710 73 1.598 31.55 20 829 8622 [Rint ) 0.1075] 403 0.940 0.0624, 0.1256

C85.67H117.5Cu4F12N14.84O20S4 2285.51 triclinic P1h 11.059(3) 22.177(5) 26(152(6) 114.566(6) 90.690(6) 99.175(6) 5737(2) 2 100(2) 0.710 73 1.323 33.48 61 339 37 393 [Rint ) 0.0627] 1540 0.888 0.1203, 0.3301

0.2296, 0.3264

0.1720, 0.1565

0.1908, 0.3788

0.920

0.830

1.020

empirical formula fw cryst syst space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 formula units/cell temp, K λ(Mo KR), Å Fcalcd, g cm-3 Θmax, deg reflns measured unique reflns param µ, mm-1 R1,a wR2b [I > 2σ (I)] R1,a wR2b (all data) GOF (F2) a

3b(CF3SO3)4‚xCH3CN

4(ClO4)4‚xCH3CN‚xH2O

C90.67H123Cu4F12N17.33O22S4 2418.13 triclinic P1h 13.1376(15) 16.701(2) 26.734(3) 105.424(3) 100.280(3) 93.037(3) 5532.6(11) 2 100(2) 0.710 73 1.452 32.63 79 963 37 559 [Rint ) 0.0369] 1480 0.927 0.0905, 0.2653

C81H115.5Cu4N14.5Cl4O25 2088.34 monoclinic C2/c 41.432(5) 12.453(2) 26.216(3) 90 127.805(5) 90 10687(3) 4 100(2) 0.710 73 1.298 33.22 78 964 19 778 [Rint ) 0.0608] 616 0.956 0.0687, 0.1795

0.1363, 0.3046

0.0864, 0.1916

1.037

1040

R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2 ]}1/2, w ) 1/[σ2Fo2 + (aP)2 + bP]i. P ) (Fo2 + 2Fc2)/3.

polyamines were among the first ligand backbones reported to create controlled cavities in which the selective recognition of cationic, anionic, or neutral molecules could take place.21-23 Despite this fact, their use as building blocks in the assembly of larger supramolecular structures has, so far, only been explored in rather limited examples.24-26 In this work, we (19) Bradbury, J. R.; Hampton, J. L.; Martone, D. P.; Maverick, A. W. Inorg. Chem. 1989, 28, 2392-2399. (20) Maverick, A. W.; Klavetter, F. E. Inorg. Chem. 1984, 23, 41294130. (21) Lindoy, L. F. The Chemistry of Macrocyclic Ligand Complexes; Cambridge University Press: Cambridge, U. K., 1992. (22) Izatt, R. M.; Pawlak, K.; Bradshaw, J. S.; Bruening, R. L. Chem. ReV. 1995, 95, 2529-2586. (23) Alexander, V. Chem. ReV. 1995, 95, 273-342.

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report the self-assembly of molecular rectangles resulting from the dimerization of dicopper hexaazamacrocyclic building blocks. Experimental Section Materials. Solvents were purchased from SDS and were of reagent grade. Acetonitrile was distilled over CaH2 and stored over molecular sieves prior to use. Diethyl ether was distilled over (24) Ki-Whan Chi, C. A.; Stang, P. J. J. Org. Chem 2004, 69, 29102912. (25) He, W.; Liu, F.; Duan, C.; Guo, Z.; Zhou, S.; Liu, Y.; Zhu, L. Inorg. Chem. 2001, 40, 7065-7071. (26) Pietraszkiewicz, M.; Pietraszkiewicz, O.; Saf, R.; Hummel, K.; Skorupa, A.; Mrozinski, J. J. Inclusion Phenom. Macrocyclic Chem. 1999, 35, 233-242.

Isomeric Molecular Rectangles Table 2. Selected Bond Lengths (Å) and Angles (degrees) for 1(CF3SO3)4, 2(CF3SO3)4, 3asyn(CF3SO3)4, 3aanti(CF3SO3)4, 3b(CF3SO3)4, and 4(ClO4)4 1(CF3SO3)4

2(CF3SO3)4

3asyn(CF3SO3)4

Cu1-O1 1.912(5) Cu1-N1 1.980(6) Cu1-N2 2.067(6) Cu2-O2 1.931(7) Cu2-N4 1.975(7) Cu2-N3 2.037(6) O1-Cu1-N1 178.1(3) O1-Cu1-N2 93.95(13) N1-Cu1-N2 85.82(13) N2-Cu1-N2 164.0(3) O2-Cu2-N4 180.0(4) O2-Cu2-N3 93.65(16) N4-Cu2-N3 86.36(16) N3-Cu2-N3 163.9(3)

Cu1-N4 2.010(4) Cu1-N2 2.029(4) Cu1-N1 2.084(4) Cu1-N3 2.096(3) Cu1-N5 2.198(4) N4-Cu1-N2 176.52(15) N4-Cu1-N1 91.72(14) N2-Cu1-N1 85.95(15) N4-Cu1-N3 95.04(15) N2-Cu1-N3 85.98(15) N1-Cu1-N3 153.96(13) N4-Cu1-N5 87.46(15) N2-Cu1-N5 95.61(14) N1-Cu1-N5 104.16(14) N3-Cu1-N5 101.24(14)

Cu1B-O3B 1.928(4) Cu1B-N2B 2.009(5) Cu1B-N1B 2.098(6) Cu1B-N3B 2.115(8) Cu2B-O1B 1.923(4) Cu2B-N5B 2.000(5) Cu2B-N6B 2.075(6) Cu2B-N4B 2.076(6) O3B-Cu1B-N2B 167.4(2) O3B-Cu1B-N1B 94.1(2) N2B-Cu1B-N1B 85.4(3) O3B-Cu1B-N3B 98.6(2) N2B-Cu1B-N3B 84.8(3) N1B-Cu1B-N3B 162.3(2) O1B-Cu2B-N5B 166.2(2) O1B-Cu2B-N6B 95.23(19) N5B-Cu2B-N6B 86.1(2) O1B-Cu2B-N4B 97.0(2) N5B-Cu2B-N4B 85.1(2) N6B-Cu2B-N4B 162.1(2)

3aanti(CF3SO3)4

3b(CF3SO3)4

4(ClO4)4

Cu1-O3 1.904(4) Cu1-N5 2.017(5) Cu1-N4 2.060(5) Cu1-N6 2.061(5) Cu2-O1 1.911(4) Cu2-N2 2.003(5) Cu2-N1 2.092(5) Cu2-N3 2.102(5) O3-Cu1-N5 166.6(2) O3-Cu1-N4 96.11(19) N5-Cu1-N4 85.3(2) O3-Cu1-N6 96.07(19) N5-Cu1-N6 86.3(2) N4-Cu1-N6 160.7(2) O1-Cu2-N2 170.0(2) O1-Cu2-N1 96.1(2) N2-Cu2-N1 85.3(2) O1-Cu2-N3 90.6(2) N2-Cu2-N3 85.6(2) N1-Cu2-N3 163.9(2)

Cu1-O8 1.916(3) Cu1-N2 1.995(3) Cu1-N1 2.059(4) Cu1-N3 2.072(4) Cu2-O1 1.924(2) Cu2-N5 1.986(3) Cu2-N4 2.079(3) Cu2-N6 2.088(3) Cu3-O4 1.923(2) Cu3-N8 2.001(3) Cu3-N7 2.058(3) Cu3-N9 2.073(3) Cu4-O5 1.924(3) Cu4-N11 1.993(4) Cu4-N12 2.085(6) Cu4-N10 2.093(6) O8-Cu1-N2 165.62(11) O8-Cu1-N1 96.94(14) N2-Cu1-N1 85.26(13) O8-Cu1-N3 97.05(14) N2-Cu1-N3 84.46(13) N1-Cu1-N3 160.76(13) O1-Cu2-N5 165.97(11) O1-Cu2-N4 98.94(13) N5-Cu2-N4 84.67(12) O1-Cu2-N6 95.20(13) N5-Cu2-N6 84.56(13) N4-Cu2-N6 161.25(11) O4-Cu3-N8 165.07(11) O4-Cu3-N7 98.30(12) N8-Cu3-N7 85.72(14) O4-Cu3-N9 95.30(12) N8-Cu3-N9 84.75(14) N7-Cu3-N9 160.33(13) O5-Cu4-N11 165.59(14) O5-Cu4-N12 99.11(18) N11-Cu4-N12 84.6(2) O5-Cu4-N10 94.79(17) N11-Cu4-N10 84.9(2)

Cu1-O1 1.9643(19) Cu1-N2 1.984(2) Cu1-N1 2.074(3) Cu1-N3 2.092(3) Cu1-O2 2.351(2) Cu2-O3 1.961(2) Cu2-N5 1.973(3) Cu2-N4 2.062(3) Cu2-N6 2.098(3) Cu2-O4 2.397(2) O1-Cu1-N2 170.86(9) O1-Cu1-N1 96.35(9) N2-Cu1-N1 86.85(10) O1-Cu1-N3 93.17(9) N2-Cu1-N3 86.44(10) N1-Cu1-N3 160.22(10) O1-Cu1-O2 61.03(8) N2-Cu1-O2 109.87(9) N1-Cu1-O2 105.83(9) N3-Cu1-O2 93.95(9) O3-Cu2-N5 177.70(10) O3-Cu2-N4 91.98(11) N5-Cu2-N4 87.29(12) O3-Cu2-N6 94.73(10) N5-Cu2-N6 85.54(11) N4-Cu2-N6 166.32(10) O3-Cu2-O4 60.01(8) N5-Cu2-O4 122.28(9) N4-Cu2-O4 101.14(10) N6-Cu2-O4 92.53(9)

sodium/benzophenone under nitrogen prior to use. Unless noted otherwise, all reagents were purchased from commercial sources and used as received. 3,6,9,16,19,22-hexamethyl-3,6,9,16,19,22-hexaazatricyclo[22.2.2.211,14]triaconta-(26),11(12),13,24,27,29-hexaene, Me2p, and 3,6,9,17,20,23-hexamethyl-3,6,9,17,20,23hexaazatricyclo[23.3.1.111,15]triaconta-1(29),11(30),12,14,25,27hexaene, Me2m,27-30 were prepared according to or through slight modifications of the published procedures.

Caution! Perchlorate salts of metal complexes with organic ligands are potentially explosive. While we have not encountered any problems, it is advisable to use only small amounts and to handle the compounds with care. Physical Measurements. FT-IR spectra were taken in a MattsonGalaxy Satellite FT-IR spectrophotometer containing a MKII Golden Gate Single Reflection ATR System. Elemental analyses were conducted in a Carlo Erba Instrument, model CHNS 1108. UV-vis spectroscopy was performed on a Cary 50 Scan (Varian) Inorganic Chemistry, Vol. 45, No. 6, 2006

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Company et al. UV-vis spectrophotometer with 1 cm quartz cells. Low-resolution electrospray mass spectra were recorded on a Bruker Biotof II spectrometer. Syntheses. Terephthalic Acid Disodium Salt. Terephthalic acid (4.56 g, 27 mmol) was added to an aqueous solution of NaOH (1.98 g in 10 mL of water, 49 mmol). The solution was filtered (to remove the excess diacid), and the disodium salt was precipitated by adding diethyl ether (50 mL) and methanol (75 mL). The product was filtered and washed with diethyl ether (4.2 g, 82%). FT-IR ν: 1561, 1383 cm-1 (COO-). Elem Anal. Calcd (%) for C8H4O4Na2 (210.09): C, 45.73; H, 1.92. Found: C, 45.36; H, 1.78. [Cu2(Me2p)(OH2)2](CF3SO3)4‚CH3CN‚H2O‚1/2Et2O,1(CF3SO3)4‚ CH3CN‚H2O‚1/2Et2O. Me2p (49.9 mg, 0.10 mmol) and Cu(CF3SO3)2 (71.9 mg, 0.19 mmol) were charged in a 10 mL flask and dissolved in 20:1 CH3CN/H2O (2.5 mL) to form a reddish-blue solution. The mixture was stirred for 30 min and then filtered through Celite. Ether diffusion after 2 days affords red rectangular plates. The solvent was decanted and the crystalline solids dried under vacuum (90.4 mg, 0.07 mmol, 70%). FT-IR ν: 3445 (OH), 1472 (CdC arom.), 1244, 1161, 1027, 635 cm-1 (CF3SO3). Elem Anal. Calcd (%) for C34H54N6Cu2O14F12S4‚CH3CN‚H2O‚1/2Et2O (1350.29): C, 33.80; N, 7.26; H, 4.78; S, 9.50. Found: C, 33.76; N, 7.12; H, 4.82; S, 9.44. UV-vis (CH3CN) λmax (): 521 (466 M-1cm-1). [Cu2(Me2m)(CH3CN)4](CF3SO3)4‚2CH3CN‚2H2O, 2(CF3SO3)4‚ 2CH3CN‚2H2O. Me2m (33.2 mg, 0.067 mmol) and Cu(CF3SO3)2 (48.6 mg, 0.13 mmol) were charged in a 10 mL flask and dissolved in 20:1 CH3CN/H2O (1.5 mL) to form a bright blue solution. The mixture was stirred for 30 min and then filtered through Celite. Ether diffusion into this solution affords blue needles. The solvent was decanted and the crystalline solids dried under vacuum (77.5 mg, 0.058 mmol, 89%). FT-IR ν: 1473 (CdC arom.), 1278, 1242, 1153, 1027, 633 cm-1 (CF3SO3). Elem Anal. Calcd (%) for C34H50N6Cu2O12F12S4‚2CH3CN‚2H2O (1336.27): C, 34.16; N, 8.39; H, 4.53; S, 9.60. Found: C, 33.88; N, 8.37; H, 4.17; S, 9.33. UVvis (CH3CN) λmax (): 623 (588 M-1cm-1). [Cu4(O2CC6H5CO2)2(Me2p)2](CF3SO3)4‚4H2O, 3(CF3SO3)4‚ 4H2O. Me2p (51.1 mg, 0.10 mmol) and Cu(CF3SO3)2 (76.2 mg, 0.21 mmol) were charged in a 10 mL flask and dissolved in 20:1 CH3CN/H2O (2.5 mL) to form a reddish-blue solution. The mixture was stirred for 30 min to allow the total formation of 1(CF3SO3)4. Then, 21.7 mg of terephthalic acid disodium salt (0.10 mmol) was added directly as a solid to the stirred solution. The resulting dark blue solution was stirred for 20 h and then filtered through Celite. Ether diffusion after 3 days affords large blue rectangles. The solvent was decanted and the crystalline solids dried under vacuum (88.9 mg, 0.040 mmol, 80%). FT-IR ν: 3511 (OH), 1615, 1340 (CdO), 1251, 1225, 1156, 1028, 635 cm-1 (CF3SO3). Elem Anal. Calcd (%) for C80H108N12Cu4O20F12S4‚4H2O (2240.27): C, 42.89; N, 7.50; H, 5.22; S, 5.73. Found: C, 42.67; N, 7.66; H, 4.99; S, 5.53. UV-vis (CH3CN) λmax (): 236 (31 750), 281 (28 490), 506 (448), 630 (664 M-1cm-1). MS (ESI) m/z: 934 (100) [3(CF3SO3)42CF3SO3]+2, 573 (75) [3(CF3SO3)4-3CF3SO3]+3. [Cu4(O2CC6H4CO2)2(Me2m)2](CF3SO3)4‚4H2O, 4(CF3SO3)4‚ 4H2O. Me2m (54.9 mg, 0.11 mmol) and Cu(CF3SO3)2 (81.9 mg, 0.22 mmol) were charged in a 10 mL flask and dissolved in 20:1 (27) Menif, R.; Martell, A. E.; Squattrito, P. J.; Clearfield, A. Inorg. Chem. 1990, 29, 4723-4729. (28) Pietraszkiewicz, M.; Gasiorowski, R. Chem. Ber. 1990, 123, 405406. (29) Llobet, A.; Reibenspies, J.; Martell, A. E. Inorg. Chem. 1994, 33, 5946-5951. (30) Clifford, T.; Danby, A. M.; Lightfoot, P.; Richens, D. T.; Hay, R. W. J. Chem. Soc., Dalton. Trans. 2001, 240-246.


Figure 1. UV-vis titration of 1(CF3SO3)4 with terephthalic acid disodium salt (0-1 equiv) in CH3CN to form 3(CF3SO3)4. Scheme 1. Schematic Diagram of the Complexes Prepared in This Work

CH3CN/H2O (2.5 mL) to form a bright blue solution. The mixture was stirred for 30 min to allow the total formation of 2(CF3SO3)4. Then, 23.3 mg of terephthalic acid disodium salt (0.11 mmol) was added directly as a solid to the stirred solution. The resulting blue solution was stirred for 20 h and then filtered through Celite. Ether diffusion after 2 days affords blue needles. The solvent was decanted and the crystalline solids dried under vacuum (101.6 mg, 0.045 mmol, 82%). FT-IR ν: 3610 (OH), 1574, 1368 (CdO), 1340 (Cd C arom.), 1247, 1225, 1158, 1028, 636 cm-1 (CF3SO3). Elem Anal. Calcd (%) for C80H108N12Cu4O20F12S4‚4H2O (2240.27): C, 42.89; N, 7.50; H, 5.22; S, 5.73. Found: C, 43.14; N, 7.76; H, 5.23; S, 5.35. UV-vis (CH3CN) λmax (): 240 (33 480), 292 (24 890), 636 (829 M-1cm-1). MS (ESI) m/z: 934 (100) [4(CF3SO3)4-2CF3SO3]+2, 573 (65) [4(CF3SO3)4-3CF3SO3]+3. Single crystals of 4(ClO4)4 suitable for X-ray diffraction analysis were obtained by slow diethyl ether diffusion into acetonitrile solutions of 4(CF3SO3)4 containing NaClO4.

Isomeric Molecular Rectangles Crystal Data Collection, Structure Solution, and Refinement Details for Compounds 1(CF3SO3)4, 2(CF3SO3)4, 3a(CF3SO3)4, 3b(CF3SO3)4, and 4(ClO4)4. Crystal structure determinations for 1(CF3SO3)4 and 2(CF3SO3)4 were carried out using a Siemens P4 diffractometer equipped with a SMART-CCD-1000 area detector, a MACScience Co rotating anode with Mo KR radiation, a graphite monochromator, and a Siemens low-temperature device LT2 (T ) -120 °C). Full sphere data collection ω and φ scans were performed. The programs used were, for data collection, Smart version 5.060 (BrukerAXS, 1999), for data reduction, Saint+ version 6.02 (Bruker AXS, 1999), and for absorption correction, SADABS (Bruker AXS, 1999). Crystal structure solution was achieved using direct methods as implemented in SHELXTL version 5.10 (Sheldrick, Universtita¨t Go¨ttingen, Germany, 1998) and was visualized using the XP program. Crystal structure determinations for 3a(CF3SO3)4, 3b(CF3SO3)4, and 4(ClO4)4 were carried out using a Bruker-Nonius diffractometer equipped with an APPEX 2 4K CCD area detector, a FR591 rotating anode with Mo KR radiation, Montel mirrors as a monochromator, and a Kryoflex low-temperature device (T ) -173 °C). Full sphere data collection ω and φ scans were performed. The programs used were, for data collection, Apex2 version 1.0-22 (Bruker-Nonius, 2004), for data reduction, Saint+ version 6.22 (Bruker-Nonius, 2001), and for absorption correction, SADABS version 2.10 (Bruker AXS, 2003). Crystal structure solution was achieved using direct methods as implemented in SHELXTL version 6.10 (Sheldrick, Universtita¨t Go¨ttingen, Germany, 2000) and was visualized using the XP program. Missing atoms were subsequently located from difference Fourier synthesis and added to the atom list. A least-squares refinement on F2 using all measured intensities was carried out using the program SHELXTL version 6.10 (Sheldrick, Universtita¨t Go¨ttingen, Germany, 2000). All non-hydrogen atoms were refined including anisotropic displacement parameters. The crystals used for structure determination contain, in most of the cases, solvent molecules, which make its manipulation extremely difficult, and also have disordered anions. Because of these difficulties, some of the data sets are complicated to collect and not of the best quality for refinement. Table 1 summarizes the crystallographic refinement parameters for complexes 1(CF3SO3)4, 2(CF3SO3)4, 3a(CF3SO3)4, 3b(CF3SO3)4, and 4(ClO4)4. A list of selected bond lengths (Å) and angles (degrees) for complexes reported in this work is collected in Table 2.

Results and Discussion Preparation of the Complexes. Reactions of the corresponding para and meta phenyl-substituted hexaazacyclophanes (Me2p and Me2m, Scheme 1) with 2 equiv of Cu(CF3SO3)2 in 20:1 CH3CN/H2O yield the solvato dinuclear CuII complexes [Cu2(Me2p)(OH2)2]4+, 1, and [Cu2(Me2m)(CH3CN)4]4+, 2. Triflate salts of the complexes could be isolated as crystalline materials by slow diethyl ether diffusion into acetonitrile solutions in 70% and 89% yields, respectively. 1(CF3SO3)4 and 2(CF3SO3)4, prepared in situ, were reacted with a para-substituted diacid aromatic linker. Fast reaction was evidenced by UV-vis spectroscopy, which revealed a quantitative disappearance of the starting dinuclear complexes after the addition of 1 equiv of the terephthalic acid disodium salt. Tetrametallic [Cu4(O2CC6H5CO2)2(Me2p)2](CF3SO3)4, 3(CF3SO3)4, and [Cu4(O2CC6H5CO2)2(Me2m)2]-

Scheme 2. ORTEP Diagram of the Cationic Portions of 1(CF3SO3)4 (Left) and 2(CF3SO3)4 (Right) along with the Schematic Representation of the Self-Assembled Rectangles 3 and 4

(CF3SO3)4, 4(CF3SO3)4, were isolated in crystalline form from these reactions in 80% and 82% yields, respectively. Interestingly, UV-vis titration of 1(CF3SO3)4 with terephthalic acid disodium salt reveals that the transformation from 1 to 3 occurs with an isosbestic point at λ ) 590 nm, without the accumulation of any reaction intermediate (Figure 1). This observation strongly suggests that, after binding of the first dicarboxylate bridge, the formation of rectangle 3 by coordination of the second terephthalate unit is a cooperatively accelerated process. The analogous titration of 2 to form rectangle 4 suggests a similar behavior (Figure S1, Supporting Information). Crystallographic Characterization of the Complexes. 1(CF3SO3)4 and 2(CF3SO3)4. The molecular structures of the dinuclear complexes were established by single-crystal X-ray analysis (Scheme 2). Unfortunately, 1(CF3SO3)4 suffers from serious solvent disorder, which prevents a discussion of the metrical parameters of the complex. Nevertheless, reliable information about the overall topology, chemical composition, and coordination geometry of metal ions could be extracted from this analysis. Crystallographic characterization of 1(CF3SO3)4 and 2(CF3SO3)4 reveals that, in both complexes, each of the copper ions are bound to three nitrogen atoms of the macrocyclic ligand, but the coordination geometry, the nature and number of external ligands, and the intramolecular Cu‚‚‚Cu distance are different. Thus, the copper ions in 1(CF3SO3)4 are square planar with a water molecule completing their coordination environment, and the copper centers are separated by 6.9 Å. Instead, 2(CF3SO3)4 is a rare example of a square pyramidal CuII complex (τ ) 0.38)31 containing two acetonitrile ligands in cis orientations per metallic ion.32 Remarkably, the acetonitrile occupying the axial position lies along a tetragonally elongated axis and the corresponding Cu-N distance is significantly longer than the one associated with the equatorially bound nitrile (∆rCu-N ∼ 0.2 Å). The Cu‚‚‚Cu distance (31) Addison, A. W.; Rao, T. N.; Reedijk, J.; Van Rijn, J.; Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 7, 1349-1346.


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Company et al. Scheme 3. Schematic Representation of the Self-Assembled Rectangles 3aanti (Left), 3asyn (Middle), and 4 (Right) with the Corresponding Metrical Parameters (Distances in Å, Angles in Degrees)a

a Bond distances and angles are obtained by considering Cu ions as the vertex of the quadrilaterals.

Figure 2. ORTEP diagram (50%) of the cationic portions of 3aanti (bottom), 3asyn (middle), and 4 (top).

is substantially elongated to 7.5 Å relative to 1. Most remarkable is the distinct shape of the respective macrocyclic cavity; a box-like shape could be easily identified in 1, which we envisioned as a potential building block for supramolecular assemblies via coordination through the Cu ions, provided self-recognition phenomena apply. However, the elongated cavity exhibited by 2 and the opposing orientations of the respective Cu coordination polyhedra render selfassembly predictions difficult. 3(CF3SO3)4 and 4(ClO4)4. Single crystals of 3(CF3SO3)4 and 4(ClO4)4 were obtained by slow diethyl ether diffusion into acetonitrile solutions of the complexes (the latter containing NaClO4), and their structures were established by X-ray crystallography (Figure 2). For compound 3, two different polymorphs were measured, 3a and 3b. Both cationic 3 and 4 adopt rectangular topologies resulting from a 2 + 2 self-assembly process. Interestingly, compound 3a crystallizes as an equimolar mixture of two isomers (3asyn and 3aanti). The isomers differ in the relative position of the carboxylate oxygen atoms bound to the metal (32) (a) Hubin, T. J.; Alcock, N. W.; Morton, M. D.; Busch, D. H. Inorg. Chim. Acta 2003, 248, 33-40. (b) Monzani, E.; Casella, L.; Zoppellaro, G.; Gullotti, M.; Pagliarin, R.; Bonomo, R. P.; Tabbi, G.; Nardin, G.; Randaccio, L. Inorg. Chim. Acta 1998, 282, 180-192. (c) Scott, M. J.; Lee, S. C.; Holm, R. H. Inorg. Chem. 1994, 33, 4651-4662. (d) Torelli, S.; Belle, C.; Gautier-Luneau, I.; Pierre, J. L.; Saint-Aman, E.; Latour, J. M.; Le Pape, L.; Luneau, D. Inorg. Chem. 2000, 39, 3526-3536. (e) Irangu, J.; Ferguson, M. J.; Jordan, R. B. Inorg. Chem. 2005, 44, 1619-1625.


ion (Figure 2), but the square planar coordination environment of the copper ions is almost superimposable in 1 and in the two isomeric forms of 3a. The relative orientation of the bridging aromatic rings differs in 3a and 4. In 3asyn and 3aanti, the rings are side to side, but they appear face to face in 4 (Figure 2). In addition, the carboxylate binds in a monodentate O η1 mode in both 3asyn and 3aanti, whereas in 4, it is bound in a O,O′:η1,η1 terminal mode. Despite the similarities in the copper coordination spheres of the isomeric forms observed for 3, 3asyn and 3aanti contain cavities with remarkably different geometric parameters. The structure of 3b is identical to the conformer 3asyn. Interestingly, the binding mode and relative orientation of the terephthalate group in 3asyn, and its topology, are reminiscent of a Pt-based rectangle recently reported by Stang et al.33 although, in that case, there is no evidence for additional isomeric rectangles analogous to 3aanti. The overall dimensions and shape of the macrocyclic entities could be extracted by considering the four coplanar metal ions as the hypothetical corners of a quadrilateral (Scheme 3). Thus, the dimensions of the rectangle in the syn isomer 3asyn are 6.8 × 10.9 Å2 and the respective angles deviate slightly from 90° (86.9° and 93.1°). 3aanti exhibits a nearly identical Cu‚‚‚Cu axis (6.8 × 11.0 Å) but exhibits distorted angles of 76.2° and 103.8°. The metal-defined quadrilateral in 4 is even less regular in shape, and the respective metrical parameters are characterized by slightly longer intramolecular (7.1 Å) and shorter intermolecular (10.7 Å) Cu‚‚‚Cu distances, as well as similarly distorted angles (77.7° and 102.3°). In this case, the Cu ions are five-coordinate and exhibit square pyramidal geometries (τ ∼ 0.18). A closer examination of the structures reveals that the unoccupied internal cavity is accessible to external molecules and could be better defined by the shortest Cu‚‚‚Cu distance and by the shortest interaromatic Car-Car distance (Figure 2). The latter is 6.3 Å in 4 and 6.5 Å in 3asyn and decreases down to 4.6 Å in 3aanti. This clearly indicates that the empty space in the cavities of 3asyn and 3aanti is substantially different, such that they could be thought of as the opened and closed isomeric forms. Interestingly, inspection of the crystalline lattice in 3a (Figure 3) reveals that 3asyn packs forming channels along the a crystallographic axis, in contrast with 3aanti, which does not form such macroscopic structures. The cationic unit in 4 also forms channels along the b axis; although in this case, they are occupied by acetonitrile molecules. (33) Das, N.; Mukherjee, P. S.; Arif, A. M.; Stang, P. J. J. Am. Chem. Soc. 2003, 125, 13950-13951.

Isomeric Molecular Rectangles

Figure 3. Space-filling diagram of 3a(CF3SO3)4 (left) along the a axis and 4(ClO4)4 (right) along the b axis showing the channels. H atoms and acetonitrile molecules have been omitted for clarity.

Figure 4. ESI-MS spectrum of 3(CF3SO3)4 in a 1:1 CH3CN/H2O solution. Simulated (top) and experimental (bottom) isotopic distributions for the cationic species [3(CF3SO3)4-3CF3SO3]3+ and [3(CF3SO3)4-2CF3SO3]2+ are shown (OTf stands for CF3SO3).

Spectroscopic Characterization of the Complexes. Molecular rectangles 3(CF3SO3)4 and 4(CF3SO3)4 were spectroscopically characterized by FT-IR and UV-vis spectroscopy. The most distinctive features of their respective IR spectra are two strong bands at 1615 and 1340 cm-1 for 3 and at 1574 and 1368 cm-1 for 4. The high-energy band is assigned to the νasym COO stretching mode, while the lowerenergy component corresponds to the corresponding νsym mode. The larger ∆(νasym - νsym) difference exhibited by 3 in comparison with 4 clearly reflects the different binding mode of the carboxylate ligand,34 as unambiguously ascertained by X-ray crystallography. On the other hand, the UV(34) (a) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds, 4th ed.; John Wiley: New York, 1986. (b) Deacon, G. B.; Phillips, R. J. Coord. Chem. ReV. 1980, 33, 227-250.

vis spectra of the four copper complexes reported in this work (Figure S2, Supporting Information) are characterized by relatively weak features between 500 and 700 nm characteristic of ligand field transitions of d9 ions.35 The energy of these features is relatively high compared with the spectroscopic behavior observed in mononuclear trigonal bipyramidal copper complexes containing tripodal amine ligands, which strongly suggests that the solid-state coordination geometries of the complexes described in this work are retained in solution.36,37 (35) Hathaway, B. J.; Billing, D. E. Coord. Chem. ReV. 1970, 5, 143207. (36) Schatz, M.; Becker, M.; Thaler, F.; Hampel, F.; Schindler, S.; Jacobson, R. R.; Tyeklar, Z.; Murthy, N. N.; Ghosh, P.; Chen, Q.; Zubieta, J.; Karlin, K. D. Inorg. Chem. 2001, 40, 2312-2322.


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Company et al. Integrity of the Rectangles in Solution. ESI-MS measurements of 3(CF3SO3)4 and 4(CF3SO3)4 in CH3CN/H2O solutions give similar results (Figure 4 and Figure 4S, Supporting Information). In both cases, the more intense peaks appear at m/z ) 934.1 and 573.0 with isotopic patterns that match the cationic species {[Cu4(O2CC6H5CO2)2L2](CF3SO3)2}2+ ([X-2CF3SO3]2+) and {[Cu4(O2CC6H5CO2)2L2](CF3SO3)}3+ ([X-3CF3SO3]3+) [X ) 3(CF3SO3)4, L ) Me2p or X ) 4(CF3SO3)4, L ) Me2m] respective formulations. The single bimetallic macrocyclic complex is not observed in the ESI-MS measurements, thus strongly suggesting that the macrocyclic tetrametallic boxes are retained in solution. In addition, cluster ions that could be identified as larger nuclearity assemblies were not observed. Conclusions The self-assembly of macrocyclic dinuclear complexes via the coordination of terephthalate bridges has led to the preparation of a new family of molecular rectangles with unprecedented isomeric diversity. These structures bear a resemblance to the cavitands prepared by the self-assembly of calixarene building blocks.38-40 The wealth of information (37) Dittler-Klingemann, A. M.; Orvig, C.; Hahn, F. E.; Thaler, F.; Hubbard, C. D.; van Eldik, R.; Schindler, S.; Fabian, I. Inorg. Chem. 1996, 35, 7798-7803.


arising from studies over the past decades on the physicochemical properties and potential applications of crown ethers and related aza analogues such as the ones employed in this work warrant a myriad of potential uses for the type of complexes herein described.21-23,26 Acknowledgment. This research has been financed by MCYT of Spain through Project BQU2000-0458. A.L. is grateful to CIRIT Generalitat de Catalunya (Spain) for the Distinction Award and the aid SGR2001-UG-291. A.C. thanks MEC for a Ph.D. grant. R.M. thanks MEC of Spain for postdoctoral support. Supporting Information Available: UV-vis spectra of the complexes reported in this work, UV-vis titration of 2 with terephthalic acid disodium salt to give 4, and ESI-MS of 4. Crystallographic data in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org. IC051759K (38) Menozzi, E.; Busi, M.; Ramingo, R.; Campagnolo, M.; Geremia, S.; Dalcanale, E. Chem.sEur. J. 2005, 11, 3136-3148. (39) Fochi, F.; Jacopozzi, P.; Wegelius, E.; Rissanen, K.; Cozzini, P.; Marastoni, E.; Fisicaro, E.; Manini, P.; Fokkens, R.; Dalcanale, E. J. Am. Chem. Soc. 2001, 123, 7539-7552. (40) Jacopozzi, P.; Dalcanale, E. Angew. Chem., Int. Ed. 1997, 36, 613615.

Isomeric Molecular Rectangles Resulting from Self-Assembly of

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